Optimization of multi-trophic aquaculture systems for <em>Penaeus monodon</em> through the introduction of Mugil cephalus, <em>Scylla serrata</em>, and Microecological Agents

Abstract

The mixed aquaculture model, developed based on the ecological principles of species' living characteristics, habits, and different requirements for matter and energy of different ecological niches, has been proven to be an environmentally efficient and low-carbon type of aquaculture. Based on this concept, the present study aims to establish an effective regulation of aquaculture water quality by determining a reasonable fish-shrimp-crab ratio and combining the use of microbial agents. The research initially establishes a multi-trophic integrated aquaculture model of shrimp-fish-crab and develops the microecological regulation of water quality in multi-trophic level aquaculture ponds. In this study, the experimental ponds were divided into one control group (shrimp) and three experimental groups (different species ratio combinations of shrimp, sea mullet and mangrove crab), each comprising three ponds, and subjected to a 60-day cultivation period. Water quality parameters such as total nitrogen, total phosphorus, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, active phosphorus, and chemical oxygen demand (COD) were monitored bi-weekly. Results showed significant reductions in these metrics within the experimental groups compared to the control group. Specifically, group 3 demonstrated the most substantial decreases, with a maximum reduction range of 32.54% to 60.09%. Shrimp growth and survival rates were notably influenced by the mixed culture system, with group 3 exhibiting the highest final yield and significant improvement in average body weight. Furthermore, introducing Sea mullet and mangrove crabs into the pond system proved beneficial for water quality and shrimp productivity. The optimal co-culture scheme was determined to be 0.90 Sea mullet/m², 0.45 mangrove crabs/m², and 75 shrimp/m². Additionally, the use of microecological agents like <em>Bacillus subtilis</em>, <em>Bacillus licheniformis</em>, and <em>Saccharomyces cerevisiae</em> further enhanced the farming environment. The optimal application scheme in the experimental ratio plan was: <em>Bacillus subtilis</em> applied at a concentration of 5.0×10^8 CFU/m³ with a frequency of once every 10 days; <em>Bacillus licheniformis</em> applied at a concentration of 1.0×10^8 CFU/m³ also every 10 days; and <em>Saccharomyces cerevisiae</em> administered at a concentration of 2.0×10^8 CFU/m³, with the same 10-day interval. This will promote the development of a sustainable and efficient integrated aquaculture model for <em>Penaeus monodon</em>, providing theoretical support and practical foundation for its application.